Mechanisms of oxygen ion diffusion in a nanoporous complex oxide 12CaO•7Al2O3 -: art. no. 014101

We performed a theoretical analysis of O2- diffusion mechanisms in a nanoporous complex oxide 12CaO center dot 7Al(2)O(3) (C12A7). This material can be viewed as a positively charged framework, arranged in subnanometer sized cages, hosting extra-framework O2- ions occupying one in six cages. Using both classical molecular-dynamics simulations and ab initio calculations we demonstrate that the diffusion of O2- species is dominated by the exchange of framework and extra-framework O2- ions rather than by an interstitial diffusion mechanism. The results allow us to rationalize the origins of the experimentally observed high oxide ion conductivity of C12A7 and the stability of its lattice under positive ion-beam irradiation.